Overdue security update alert won't go away!

I am puzzled by an overlay icon (exclamation point inside of a triangle - just like the one posted along side this post title) on top of my taskbar Zone Alarm icon that is an alert for, "overdue security update". When I open the ZA window and click on update, the message reads, "You are up to date", but the "overdue update alert" icon remains.

Why is this icon there in the first place and how do I get rid of this icon?

ZA Security Update Overdue?!

I have the ZoneAlarm Free Firewall (no antivirus). Yet just now upon moving my mouse over the ZA icon in the quick launch area it says that a security update is overdue. I've tried checking ZA for updates & it doesn't find any.